Method of staining embossing plates



Patented May 19, 1953 METHOD OF STAINING EMBOSSING PLATES Howard M.Gadbcrry' and Erik Peterson, Kansas City, Mo.,. rated, Kansas Gity,souri.

assignors to Hall Brothers Incorpo- Mo., a. corporation of Mis:-.

N Drawing. Application August 27,, 1951, Serial No. 243,926

3' Claims.

This invention relates. to a metal stain and method of using same in thepreparation of em,- bossing plates and more particularly to a solutionand its use for staining brass in the wax trans,-

fer of designs in the preparation for-engraving of brass. The transferis currently made as follows:

The design is scribed on either gelatin or transparent plastic sheetingand dusted and rubbed with tale. The brass plate is prepared by coatingit with an asphaltum engravers ground which is essentially bituminousresist. The scribed sheeting is faced against the coated brass andrubbed to transfer the tale to the engravers ground.v The White linesleft by this process are again scribed with a point and the brasselectrolytically etched in a salt bath or by a, chemical etch until therequired lines have been etched into the brass. The asphaltum engraversground is then removed with thinner and the plate is ready for theengraving process.

The objects of the present invention are to provide a brass stainsolution for use in wax: transfer of designs to brass plates in thepreparation for engravin same to form embossing plates or dies; to.provide such a brass stain solution which is stable in storage and use;to provide a, stain which will not strike through a wax coating but willprovide a stain on uncoated areas which will contrast with the brass soas to be easily visible in fine lines and suficiently durable to resistremoval during handling; to provide a stain for brass which isrelatively rapid in action, preferably staining the brass in less thanone minute, reproducing fine lines and delicate detail; and to provide abrass stain and method of using same with a wax transfer for reductionin time required in transferring a design to a brass'plate.

We have found that salts of certain noble metals are of such characteras to be particularly effective in staining uncoated areas of metalplates having surfaces in the active state such as, are. used forengraving of embossing plates or dies, and the salts of noble metals donot penetrate or strike through a transfer Wax coating on such plates.Examples of salts of noble metals having desired stainingcharacteristics are chloroplatinic acid, bromoplatinic acid, platinumtetrachloride, platinum sulphate, chloroauric acid, bromoauric acid,gold chloride, palladium chloride, and palladium sulphate. Certain saltsof gold, platinum, and palladium are not useable, notably the cyan-idessuch as gold cyanide and the like, which lay down bright gold instead offinely divided black deposits or stain. While these various salts ofnoble metals are satisfactory, for economy and efficiency we prefer touse gold chloride in the metal stain and process.

The metal stain preferably consists ina solution of gold chloridecrystals (AuCLaHClBI-IZO) and distilled water. An example of theproportions of the solution is two (2) grams of gold chloride crystals(AuCIc.I-ICl=.3HzO) and one thousand (1000) cc. distilled water. It ispreferred that the proportions of the ingredients used in preparing thesolution be kept within plus or minus ten percent (:10 of this example.The solution, mixed in these proportions, preferably should be stored ina tightly stoppered, amber glass bottle or other suitable containeruntil required for use. The solution is light stable, however, andthesolution in use may be kept in a covered glass vessel on the work tablewithout fear of decomposition.

In the actual staining process for brass engraving plates, arectangular, flat-bottomed glass dish, fitted with a matching glasscover, has been found to be very advantageous for staining by thedipping process. Enough of the brass stain solution should be placed inthe staining dish topro videa suitable depth of the solution, forexample approximately one-fourth of an inch. The design is scribed on atransparent gelatin o plastic sheeting and the resulting burr around thescribed lines is removed by scraping, usually with the out edge ofanother plastic sheet. A suitable transfer wax is employed to deposit awax coating on the transparent plastic sheet everywhere exceptonthescribed lines. Transfer wax is usually a soft, pliable wax,somewhat softer than beeswax, and in use the transfer wax is warmedbetween the hands until it is quite pliable and then it is rolled overthe surface of the transparent plastic sheet to deposit a thick, dullcoating of wax. When a suitable wax coating has been applied to thescribed sheet, the sheet is faced against a polished surface of a cleanbrass plate and thereverse side of the sheet rubbed with a smoothbrushing tool, using considerable pressure. Theback of the scribed sheetis lubricated with a few drops of oil to prevent damage to the sheet.When the plastic sheet is removed from the brass plate, a comparativelyuniform coating of wax has been transferred everywhere except where thefine lines had been scribed in the plastic sheet. This application ofthe wax to the brass plate provides a clean polished surface of theplate exposed in areas corresponding to the design scribed on theplastic sheet and such a clean surface is necessary to obtain thestaining of sharp lines and the like on said plate. The brass plate tobe stained should be protected by wax coating around the wax transferand on the four edges. The back need not be wax coated.

To facilitate dipping, a suction cup may be affixed to the back of thebrass plate. This allows easy handling of the brass plate so that it canbe clipped without wetting the back of the plate and avoids holding thebrass plate in the fingers while dipping. The gold chloride solution,while harmless to the hands, will stain the fingers blue near the spotat which they contact the brass, such stain consisting of purplishcolloidal gold which is hard to remove.

The coated brass plate is dipped into the staining solution to asuitable depth, for example approximately one-eighth of an inch. Careshould be taken not to entrap air under the surface of the brass plateand to obtain good contact with the solution. Approximately fifteen tothirty seconds is required for the deposition of a good black stain inthe lines. After the brass plate is removed from the staining solution,the plate should be rinsed with water and the wax coating removed with asuitable solvent.

The concentration of approximately two grams of gold chloride per literof water is preferred because it gives a good black stain in areasonable time and the adherence of stain deposited more slowly fromweak solutions is better than that of stains deposited quickly in moreconcentrated solutions. However, as more plates are stained the goldcontent of the solution will be progressively exhausted and eventuallythe staining process will require too long to be practical. If the .tipof a clean strip of polished brass does not turn black in the stainsolution Within one minute, the solution should be considered exhaustedand discarded as the amount of gold lost by discarding such solutionwill be so slight as to make recovery of it not worthwhile.

The brass plate used for engraving should have a polished surface thatis clean and free from grease or dirt before the wax transfer is appliedto it. The brass surface should be in the active state, that is, asurface that has been mechanically polished,

The brass stain solution is non-toxic and has no odor. The solution isstable in storage and use and is also economical despite the fact thatgold is used therein. When used to stain brass it provides a black stainthat reproduces fine lines and delicate detail, with such contrast tothe brass surface as to be easily visible. Also the stain is verydurable and is not removed by handling during the engraving process.

We have specifically described the process with reference to a metalstain having gold chloride therein, but the same process may be usedwith stains havin one of the other namedsalts of noble metals therein,as each is capable of use with the wax transfer process to produce sharplines and good resolution.

What we claim and desire to secure by Letters Patent is:

1. The method of staining designs on brass plates in the preparation forengraving of embossing plates consisting of, scribing a design on apliable plastic sheet, scraping any burrs from around the scribed lines,applying a transfer wax coating onto the surface of the plastic sheetbut not on the scribed lines, placing the wax coated sheet on a polishedsurface of a brass plate, rubbing the other side of the plastic sheet totransfer the wax coating thereof onto the brass plate except where thedesign has been scribed in the plastic sheet to leave clean exposedareas of the brass plate corresponding to the design to be reproduced,contacting the wax coated brass plate with a staining solution includinga salt of a noble metal selected from the group consisting ofchloroplatinic acid, bromoplatinic acid, platinum tetrachloride,platinum sulphate, chloroauric acid, bromoauric acid, gold chloride,palladium chloride and palladium sulphate to stain the exposed areas ofthe brass plate, and removing the wax coating from the brass plate witha suitable solvent to present a clean surface with the design stainedthereon.

2. The method of staining designs on brass plates in the preparation forengraving of embossing plates consisting of, scribing a design on atransparent plastic sheet, scraping any burrs from around the scribedlines, rolling a transfer wax onto the scribed surface of the plasticsheet to deposit a thick wax coating thereon, placing the wax coatedsheet on a polished surface of a brass plate, rubbing the other side ofthe plastic sheet to transfer the wax coating thereof onto the brassplate except where the design has been scribed in the plastic sheet toleave clean exposed areas of the brass plate corresponding to the designto be reproduced, contacting the wax coated brass plate with a stainingsolution including gold chloride to stain the exposed areas of the brassplate, rinsing the plate with water, and removing the wax coating fromthe brass plate with a suitable solvent to present a clean surface withthe design stained thereon.

3. The method of staining designs on metal plates in the preparation forengraving of embossing plates consisting of, applying a transfer waxcoating to a polished surface of a metal plate, said wax coating havingcutout portions corresponding to a design to be reproduced to exposecorresponding areas of the polished surface of the metal plate,contacting the exposed areas of the polished metal surface with a goldchloride solution to stain said, exposed areas, and removing the waxcoatin from the metal plate with a suitable solvent to present a cleansurface with the design stained thereon.

HOWARD M. GADBERRY. ERIK PETERSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,988,012 Mason Jan. 15, 1935 2,221,641 Knapp Nov 12, 19402,448,857 Brice Sept. 7, 1948 2,516,986 Heinse Aug. 1, 1950

1. THE METHOD OF STAINING DESIGNS ON BRASS PLATES IN THE PREPARATION FORENGRAVING OF EMBOSSING PLATES CONSISTING OF, SCRIBING A DESIGN ON APLIABLE PLASTIC SHEET, SCRAPING ANY BURRS FROM AROUND THE SCRIBED LINES,APPLYING A TRANSFER WAX COATING ONTO THE SURFACE OF THE PLATIC SHEET BUTNOT ON THE SCRIBED LINES, PLACING THE WAX COATED SHEET ON A POLISHEDSURFACE OF A BRASS PLATE, RUBBING THE OTHER SIDE OF THE PLASTIC SHEET OFTO TRANSFER THE WAX COATING THEREOF ONTO THE BRASS PLATE EXCEPT WHERETHE DESIGN HAS BEEN SCRIBED IN THE PLASTIC SHEET TO LEAVE CLEAN EXPOSEDAREAS OF THE BRASS PLATE CORRESPONDING TO THE DESIGN TO BE REPRODUCED,CONTACTING WAX COATED BRASS PLATE WITH A STAINING SOLUTION INCLUDING ASALT OF A NOBLE METAL SELECTED FROM THE GROUP CONSISTING OFCHLOROPLATINIC ACID, BROMOPLATINIC ACID, PLATINUM TETRACHLORIDE,PLATINUM SULPHATE, CHLOROAURIC ACID, BROMOAURIC ACID, GOLD CHLORIDE,PALLADIUM CHLORIDE AND PALLADIUM SULPHATE TO STAIN THE EXPOSED AREAS OFTHE BRASS PLATE, AND REMOVING THE WAX COATING FROM THE BRASS PLATE WITHA SUITABLE SOLVENT TO PRESENT A CLEAN SURFACE WITH THE DESIGN STAINEDTHEREON.